Involvement of Smad pathway in proteoglycan 4 expression induced by hydrostatic pressure in temporomandibular synovial fibroblasts / 中华口腔医学杂志

ABSTRACT

<p><b>OBJECTIVE</b>To examine the expression of proteoglycan 4 (PRG-4) induced by hydrostatic pressure in rat temporomandibular synovial fibroblasts and investigate the possible mechanism.</p><p><b>METHODS</b>The cultured rat temporomandibular synovial fibroblasts were subjected to 100 kPa magnitude intermittent hydrostatic pressure (IHP) at frequency of 4 h/day, and the static group served as control. The expressions of Smad pathway proteins and p38MAPK pathway proteins were analyzed by Western blot and immunofluorescence staining. Then the cells were incubated with SB431542, the inhibitor of transforming growth factor (TGF)-β receptor. Western blot and reverse transcription PCR were used to detect the PRG-4 expression after 72 h.</p><p><b>RESULTS</b>The expression of phosphorylated Smad-2 and phosphorylated Smad-3 were increased after 1 h of IHP, reaching a maximum after 2 h and 4 h of IHP, respectively.However, the protein content of phosphorylated p38 did not vary significantly. In addition, IHP induced nuclear translocation of Smad-2/-3, and the immunofluorescence staining signal intensity markedly increased (24.11 ± 4.70)(P < 0.05). The levels of PRG-4 mRNA were significantly increased by IHP (1.48 ± 0.08)(P < 0.05). Treatment of cells with SB431542 could decrease the expression of PRG-4 mRNA significantly after IHP (0.47 ± 0.05)(P < 0.05). In addition, SB431542 inhibited the expression of PRG-4 protein induced by IHP.</p><p><b>CONCLUSIONS</b>Smad signal acts as an essential signal pathway to regulate PRG-4 expression induced by IHP.</p>